title: Enzymes immobilized in mesoporous silica: a physical-chemical perspective.
abstract: Mesoporous materials as support for immobilized enzymes have been explored extensively during the last two decades, primarily not only for biocatalysis applications, but also for biosensing, biofuels and enzyme-controlled drug delivery. The activity of the immobilized enzymes inside the pores is often different compared to that of the free enzymes, and an important challenge is to understand how the immobilization affects the enzymes in order to design immobilization conditions that lead to optimal enzyme activity. This review summarizes methods that can be used to understand how material properties can be linked to changes in enzyme activity. Real-time monitoring of the immobilization process and techniques that demonstrate that the enzymes are located inside the pores is discussed by contrasting them to the common practice of indirectly measuring the depletion of the protein concentration or enzyme activity in the surrounding bulk phase. We propose that pore filling (pore volume fraction occupied by proteins) is the best standard for comparing the amount of immobilized enzymes at the molecular level, and present equations to calculate pore filling from the more commonly reported immobilized mass. Methods to detect changes in enzyme structure upon immobilization and to study the microenvironment inside the pores are discussed in detail. Combining the knowledge generated from these methodologies should aid in rationally designing biocatalyst based on enzymes immobilized in mesoporous materials.
authors.affiliation: Chalmers University of Technology, Department of Chemical and Biological Engineering, Physical Chemistry, 412 96 Gothenburg, Sweden.
authors.forename: Nils
authors.initials: N
authors.lastname: Carlsson
authors.affiliation: Chalmers University of Technology, Department of Chemical and Biological Engineering, Applied Surface Chemistry, 412 96 Gothenburg, Sweden.
authors.forename: Hanna
authors.initials: H
authors.lastname: Gustafsson
authors.affiliation: Chalmers University of Technology, Department of Chemical and Biological Engineering, Industrial Biotechnology, 412 96 Gothenburg, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: Thörn
authors.affiliation: Chalmers University of Technology, Department of Chemical and Biological Engineering, Industrial Biotechnology, 412 96 Gothenburg, Sweden.
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Olsson
authors.affiliation: Chalmers University of Technology, Department of Chemical and Biological Engineering, Applied Surface Chemistry, 412 96 Gothenburg, Sweden. Electronic address: kh@chalmers.se.
authors.forename: Krister
authors.initials: K
authors.lastname: Holmberg
authors.affiliation: Chalmers University of Technology, Department of Chemical and Biological Engineering, Physical Chemistry, 412 96 Gothenburg, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Åkerman
mesh_terms: D000327:Adsorption; D002627:Chemistry, Physical; D004789:Enzyme Activation; D004798:Enzymes / Q000737:chemistry* / Q000378:metabolism; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010316:Particle Size; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D004798:Enzymes; D004800:Enzymes, Immobilized; D012822:Silicon Dioxide
keywords: Biocatalysis; Enzyme immobilization; Mesoporous silica; Microenvironment; Pore filling